I'm running some additional wiring behind the passenger's side front corner trim piece up to the overhead cabinet for some switches. Having already run a pair of wires for USB's and a voltmeter up to the cabinet, I know that I will need to open up more clearance room between the edge of the plywood and the trailer shell. The bottom surface of the plywood rests on the undercut sculpture line of the shell, so I can't just drill down near the edge of the plywood without drilling through the shell at the lip of the undercut.

I was hoping to simply remove the piece of plywood from the dinette bench seat and get it out of the trailer and away from the shell so I could easily drill holes for the wires. There's quite a bit of room to open up a pass-through in the plywood and still have it be hidden by the corner trim piece - you can see the outline of the bottom of the trim piece marked in the photo. I removed all the square drive wood screws holding the plywood to the framing, but the plywood refuses to lift up. It feels like maybe the right edge is glued to the framing above the end of the bench seat, and maybe part of the long edge as well - or maybe I missed some screws? If it is glued, I won't disturb things by prying it loose, but am just wondering if anyone has run into this before and might know why the plywood won't come free.

I removed the fixed plywood piece from both sides of our 19' to frame some storage and originally thought it was glued down or attached to the vinyl or exterior shell. Just like you, I removed all of the screws but the plywood was mysteriously stuck. I carefully checked for any other attachment points and then pulled up hard and discovered a few thin invisible staples were holding it in place. Installed the storage stops, reinforced a seat board and reinstalled the plywood without any issues.

Granted our trailer is older and they used OSB on the benchtops, but construction looks similar. I recall finding a couple of screws I missed when one side wouldn't come loose. There were a lot of screws. Sometimes they are countersunk deeper than they should be into and the wood fibers start to crowd the hole over top of the screw making them hard to see. They may have started to use glue in newer trailers but I doubt it. I did pretty large holes for a drain and power line down the passenger side and refrigerant lines down the driver's side when I did my mini-split A/C system. I recall actually doing one of my holes with the board in place and just drilled small holes carefully on the outboard area along the outline, missing the shell, and then breaking away the wood. This would be more difficult with the true plywood that you have but could be done. Since the vinyl wall covering comes down behind the bench along the perimeter I do know it is not in anyway attached directly to the trailer shell.

Thanks everyone for the responses. I'll dig out my little Stanley Wonder Bar and give it a pry. I was just hesitant to reef on the plywood till I broke something - nice to know what's really going on there.

Yep - 3 little finishing nails - 2 along the rear side and 1 into the horizontal 1x3 crosspiece toward the front. Assume they were there to keep the plywood positioned while the wood screws were installed?